<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>

  <body>
    <style>
      .nihao::before {
        content: "你好";
        display: block;
      }
    </style>
    <div class="nihao" id="nihao">Tom</div>

    <script>
      const content = window.getComputedStyle(nihao, "before")["content"];
      console.log(content);
    </script>
  </body>
</html>
